Phenylenedi(oxyacetic acid) can be prepared by several methods. U.S. Pat. Nos. 4,238,625 and 4,935,540 describe one method of preparing phenylenedi(oxyacetic acid) through the oxidation of aryloxyethanols. JP 3204833, JP 4091052 and JP 4173765 describe the preparation of phenylenedi(oxyacetic acid) from resorcinol and chloroacetic acid.
U.S. Pat. No. 4,440,922 describes the polyester homopolymers made from phenylenedi(oxyacetic acid). However, homopolymers made from phenylenedi(oxyacetic acid) are amorphous and have low glass transition temperatures making these polyesters difficult to dry. They polyesters have low elongations and are consequently brittle. In general, homopolymers made from phenylenedi(oxyacetic acid) are unsuitable for use in rigid containers.
U.S. Pat. Nos. 4,440,922, 4,552,948, 4,663,426, and 5,030,705 describe the use of copolyesters containing phenylenedi(oxyacetic acid) for containers. These copolyesters have low permeability. However, because of the high level of modification, these copolyesters are difficult to crystallize. The poor crystallization behavior of these copolyesters makes them difficult to dry and limits the amount of strain induced crystallization that occurs during container fabrication. Low levels of crystallinity in the containers often result in poorer mechanical properties and lower gas barrier.
U.S. Pat. No. 5,239,045 describes copolyesters containing terephthalic acid, ethylene glycol and 0.5 to 4.5 mole % of phenylenedi(oxyacetic acid). The gas barrier properties of these copolyesters are not sufficient to meet the requirements of many container applications including beer and small soft drink containers.
U.S. Pat. No. 4,959,421 describes blends of PET with copolyesters containing isophthalic acid, naphthalenedicarboxylic acid and phenylenedi(oxyacetic acid). In these gas barrier materials disclosed in the above-described specification, however, the barrier level is low and in order to produce a container having a sufficient gas barrier property, it is necessary to make the barrier layer thick. The total thickness of the container is, therefore, inconveniently increased. In addition, the copolyesters in the above-described specification are immiscible with PET; thus, blends of the copolyesters with PET can be hazy which is undesirable in many container applications.
The above-mentioned prior art polyesters and copolyesters comprising phenylenedi(oxyacetic acid) exhibit poor crystallinity and gas barrier properties. The present invention overcomes the problems of poor crystallization and/or gas barrier properties by providing a novel copolyester blend containing phenylenedi(oxyacetic acid) with improved gas barrier properties.